The present invention relates to an apparatus for and a method of mixing a plurality of materials, specifically powders, to supply a mixture having a required homogeneity.
The present invention provides a mixing apparatus for supplying a mixture having a required homogeneity, comprising: a mixing device for mixing a plurality of materials, the mixing device including a mixing vessel and having at least one inlet port and an outlet port; a supply line connected to the outlet port of the mixing device; and at least one measuring device for measuring on-line at at least one point in the supply line the composition of the mixed material passing in use through the supply line.
Preferably, the at least one measuring device is configured to measure on-line the composition of the mixed material passing in use through the supply line at a plurality of points in the supply line.
In a preferred embodiment the mixing apparatus comprises a plurality of measuring devices for measuring on-line at a plurality of points in the supply line the composition of the mixed material passing in use through the supply line.
Preferably, one measurement point is at the inlet end of the supply line.
Preferably, one measurement point is at the outlet end of the supply line.
In a particularly preferred embodiment one measurement point is at the inlet end of the supply line and another measurement point is at the outlet end of the supply line.
Preferably, the mixing apparatus further comprises at least one flow diversion mechanism for selectively diverting from at least one point in the supply line mixed material passing in use through the supply line which is measured as not having the required homogeneity. More preferably, the at least one diversion point is downstream of the upstreammost measurement point.
In a preferred embodiment the mixing apparatus comprises a plurality of flow diversion mechanisms for selectively diverting from one or more of a plurality of points in the supply line mixed material passing in use through the supply line which is measured as not having the required homogeneity.
Preferably, each diversion point is downstream of a respective measurement point.
In a particularly preferred embodiment each flow diversion mechanism comprises a valve disposed in the supply line, the valve having an inlet port and a first outlet port connected in the supply line and a second outlet port through which mixed material measured as not having the required homogeneity is in use diverted.
Preferably, the mixing apparatus further comprises a transfer line into which mixed material measured as not having the required homogeneity is in use diverted.
More preferably, at least a section of the transfer line is configured such that the mixed material diverted thereinto can flow by gravitational flow therethrough.
Preferably, the second outlet port of each valve is connected to the transfer line.
Preferably, the mixing apparatus further comprises a flow control mechanism for causing the mixed material to flow through the supply line.
In one embodiment the flow control mechanism is a feed mechanism for feeding the mixed material through the supply line.
In another embodiment the supply line is configured such that the mixed material can flow by gravitational flow therethrough and the flow control mechanism is a valve for selectively permitting the mixed material to flow through the supply line.
Preferably, the supply line is substantially vertically directed.
Preferably, the mixing apparatus further comprises a plurality of supply vessels for containing separately the materials to be mixed in the mixing vessel of the mixing device and a further supply vessel for containing a mixture of the materials to mixed, the supply vessels being connected to the at least one inlet port of the mixing device by respective feed lines which each include a flow control mechanism operable to meter per unit time to the mixing device amounts of the respective materials to be mixed and the mixture of the materials to be mixed.
More preferably, the mixing apparatus further comprises a further measuring device in the feed line connected to the further supply vessel for measuring the composition of the mixed material passing in use through the feed line connected to the further supply vessel.
Preferably, at least one of the at least one measuring device is a spectroscopic measuring device.
More preferably, the spectroscopic measuring device is one of a reflectance, transflectance or transmission device.
In one preferred embodiment the spectroscopic measuring device is an infra-red spectrophotometer.
In another preferred embodiment the spectroscopic measuring device is a near infra-red spectrophotometer.
In yet another preferred embodiment the spectroscopic measuring device is an x-ray spectrophotometer.
In still another preferred embodiment the spectroscopic measuring device is a visible light spectrophotometer.
In a further preferred embodiment the spectroscopic measuring device is a raman spectrophotometer.
In a yet further preferred embodiment the spectroscopic measuring device is a microwave spectrophotometer.
In a still further preferred embodiment the spectroscopic measuring device is a nuclear magnetic resonance spectrophotometer.
Preferably, at least one of the at least one measuring device is a polarimeter.
Preferably, the mixing vessel of the mixing device is a non-rotating vessel.
In one embodiment the mixing device is a continuous mixer.
In an alternative embodiment the mixing device is a batch mixer.
The present invention also provides a method of supplying a mixture having a required homogeneity, comprising the steps of: introducing a plurality of materials to be mixed into a mixing vessel of a mixing device; mixing the plurality of materials in the mixing vessel; supplying mixed material from an outlet port of the mixing device through a supply line; and measuring on-line at at least one point in the supply line the composition of the mixed material passing through the supply line.
In a preferred embodiment the method comprises the step of measuring on-line at a plurality of points in the supply line the composition of the mixed material passing through the supply line.
Preferably, one measurement point is at the inlet end of the supply line.
Preferably, one measurement point is at the outlet end of the supply line.
In a particularly preferred embodiment one measurement point is at the inlet end of the supply line and another measurement point is at the outlet end of the supply line.
Preferably, the method further comprises the step of diverting from at least one point in the supply line the mixed material passing through the supply line which is measured as not having the required homogeneity.
More preferably, the at least one diversion point is downstream of the upstreammost measurement point.
In a preferred embodiment the method comprises the step of selectively diverting from one or more of a plurality of points in the supply line the mixed material passing through the supply line which is measured as not having the required homogeneity.
Preferably, each diversion point is downstream of a respective measurement point.
In one embodiment the materials to be mixed are introduced continuously into the mixing vessel.
Preferably, the method further comprises the step of transferring the mixed material diverted from the supply line to a further vessel.
More preferably, the step of introducing the materials to be mixed into the mixing vessel of the mixing device comprises the step of selectively metering per unit time to the mixing device amounts of the mixed material from the further vessel and the respective materials to be mixed and further comprising the step of measuring on-line the composition of the mixed material metered from the further vessel such that amounts of the respective materials to be mixed can be separately selectively metered to the mixing device in addition to mixed material metered from the further vessel so as to achieve the required composition.
In an alternative embodiment the materials to be mixed are introduced as a batch into the mixing vessel of the mixing device.
Preferably, the mixing vessel of the mixing device is a non-rotating vessel.